OP, everything can happen and who knows you may end up very happily married BUT are you sure she will not go into shock if you tell her? Have you ever feel that she loked at you anything but nephew? She was in family for a very long time. My cousins FIL who was her MIL second husband and was much younger then her,divorced her at some point. I saw them only few times when they were married. Couple years ago I met him in a store. We talked, regular talk, how is this, how is that. Then we exchanged numbers. He was always very friendly toward my family and numbers exchange felt totally normal. I called my parents to let them know who I met and then he called me. He asked me not to tell my parents about our relationship!!!!!!
I was in shock. I though I misunderstood but he actually asked me out.
Needless to say that I never went with him and never spoke on a phone with him anymore. The truth is that if he wouldnot be in a family I would go with him, he is pretty attractive and interesting to talk to BUT he was part of the family and even so we are not related in any ways, it is totally weird to me. And guess what, over family holiday when MIL was there and we all talked about him, myparents said that I met him and she asked me right away if he made a move.
I lied. I could feel in her voice that she would be hurt even so they were together so many years ago.
So the moral is, you may look at her as a woman, she may see just a relative in you.
Back to school next Monday! 
Who knows? They could be soooooul-mates.
Good luck!
